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# CE- 416 Truss & Frame

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Name: Md. Neshar Ahmed Limon
4th year, 2nd semester
ID: 10.01.03.151
Sec: C
Ahsanullah University of Science & Technology

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### CE- 416 Truss & Frame

1. 1. Presented To  Sabreena Nasrin B.Sc. Engg. (Civil), BUET Lecturer at Ahsanullah University of Science & Technology Presented By  Md. Neshar Ahmed Student ID: 10.01.03.151 4th Year, 2nd semester &  Munshi Galib Muktadir B.Sc. Engg. (Civil), BUET Lecturer at Ahsanullah University of Science & Technology Department of Civil Engineering Ahsanullah University of Science & Technology
2. 2.  A truss is a structure composed of slender members joined together at their end points. Planar trusses lie in a single plane. Typically a truss is a joint framed structure which is designed to sustain inclined, vertical or horizontal loads occurring at or between its points of supports and has the following characteristics:  Straight Members Members connected at their intersections by means of frictionless pins or hinges Members so arranged that the truss is loaded only at the joints Typical figure of Truss & Frames
3. 3.  Pitched Truss- Characterized by its triangular shape. It is most often used for roof construction.  Parallel Chord Truss- Its named from its parallel top and bottom chords. It is often used for roof construction.
4. 4. Flat Truss Queen Post Truss King Post Truss Lenticular Truss Bowstring Truss Lattice Truss
5. 5. The analysis of trusses is usually based on the following simplifying assumptions:  The centroidal axis of each member coincides with the line connecting the centers of the adjacent members and the members only carry axial force. All members are connected only at their ends by frictionless hinges in plane trusses. All loads and support reactions are applied only at the joints.
6. 6. Method of Joints Method of Joints: The axial forces in the members of a statically determinate truss are determined by considering the equilibrium of its joints. Tensile(T) axial member force is indicated on the joint by an arrow pulling away from the joint. Compressive(C) axial member force is indicated by an arrow pushing toward the joint.
7. 7. Effect of tension vs. compression on member sizes Potential for stress reversal Potential buckling failure modes and approaches to preventing Overall lateral stability (lateral- torsional buckling) Member redundancy: Determinate vs. Indeterminate Trusses
8. 8. Truss Determinacy Formula n = 2j – 3 →for determinacy „ n = Number of truss bars „ j = Number of joints n > 2j -3 →indeterminate n < 2j -3 →unstable
9. 9. Some renowned Trussed Structures Eifel Tower
10. 10.  Multi forced members are generally known as Frames.  Frames are commonly used to support various external loads. Figure of Frames
11. 11. Advantageous features of Framed structure 1. Speedy construction due to simplicity in geometry –consist of only columns and beams (or partially by the floor slab) as the main structural elements 2. Very rigid and stable –able to resist tremendous vertical (dead load) and lateral loads (wind) 3. Reduced dead load –absent of thick shear wall etc. 4. Roofed over at an earlier stage –every floor slab being finished becomes an cover to protect the lower floors from sun and rain 5. Offer large unobstructed floor areas –without obstacle between columns 6. Flexible utilization of space
12. 12. Advantages features of Framed structure (continued) 7. Adaptable to almost any shape 8. Easily altered within limits of frame –regular or non-regular grid system is very adaptable in spatial arrangement 9. Offsite preparation possible –especially for prefabricated construction using pre-cast concrete or structural steel elements 10. May be designed to accommodate movement 11. Acceptable distribution of natural light –window openings can be provided easily on eternal walls 12. Easy to design structurally including computer design –again, due to simple geometry
13. 13. Principle factors affecting choice of frame Structural Design consideration  Foundation consideration  Standardization of members or design  Span and floor loads  Fire resistance requirement  Maintenance consideration  Integration of architectural & structural elements
14. 14. Features of In-situ concrete frame construction Construction aspects 1. In-situ concrete is inconsistent in quality in performance -mixing, delivery, placing and compacting of concrete require very tight quality control 2. Overlapping formwork, steel fixing and concreting process make site operations more difficult –these works are to be done almost at the same time at the same location 3. Formwork erection is often timely, expensive, environmental unfriendly and labour intensive 4. Increase a lot of wet-work –difficult to maintain site in a clean and tidy environment
15. 15.  Draw the FBD of the frame or machine and its members as necessary.  Then identify any two-forced members  For a joint with more than two members or an external force, it is advisable to draw a FBD of the pin.
16. 16. Some Examples Framed Structures
17. 17. DIFFERENCE BETWEEN TRUSSES AND FRAMES Trusses Frames Members are subjected to tension/compression only At least one member is subjected to bending, shear or torsion Composed of rods Composed of bars Usually more simple to calculate, more weight effective Usually more simple to manufacture, and to place in tight layout
18. 18. DIFFERENCE BETWEEN TRUSSES AND FRAMES Connection by riveting, moment-resistant
19. 19. DIFFERENCE BETWEEN TRUSSES AND FRAMES Connection by welding, momentresistant
20. 20.  Cost Effective  Can be installed quickly even without heavy equipment to lift it into place  Unique properties of a triangular object allow trusses to span across longer distances  A triangular truss maintains its shape, preventing shift and sag. Thus giving stability to the structure.  The shape of a triangle allows all of the weight applied to the sides to be redistributed down and away from the centre.